1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method.
2. Description of the Related Art
There has been known an image recording device that records an image by repetitively performing scanning and recording operations and sub scanning. In the scanning and recording operations, the image recording device discharges ink while relatively moving a recording head with respect to a unit region of a recording medium. The recording head includes a discharge port array in which a plurality of discharge ports for discharging ink is arrayed. In the sub scanning, the recording medium is conveyed. In such an image recording device, there has been known a so-called multipass printing method of forming an image by performing the scanning and recording operations with respect to the unit region a plurality of times. In a conventional multipass printing method, using image data including one-bit information that defines discharge or non-discharge of ink for each pixel, and a plurality of mask patterns each including one-bit information that defines permission or non-permission of ink discharge for each pixel, and respectively corresponding to a plurality of times of scanning, recording data to be used for performing recording through the plurality of times of scanning is generated by dividing the image data into the plurality of times of scanning.
Furthermore, in recent years, there has been also known the technique of generating recording data using image data including multiple-bit information that can define a plurality of patterns of the numbers of ink discharge times for each pixel, and a plurality of mask patterns each including multiple-bit information that defines the number of ink discharge permitted times for each pixel, and respectively corresponding to a plurality of times of scanning. By generating the recording data in the above-described manner, ink can be discharged onto one pixel region a plurality of times. For example, Japanese Patent Application Laid-Open No. 2003-175592 discloses generating recording data using image data and mask patterns each including two-bit information.
On the other hand, there has been conventionally known image quality deterioration that occurs in the following manner. Specifically, ink of a predetermined color bleeds at an edge region where a region onto which recording has been performed using the ink of the predetermined color (an object) contacts a region onto which recording has been performed using ink of another color, a blank region onto which no recording has been performed, or the like. Such bleeding deteriorates image quality. To solve such image quality deterioration, Japanese Patent Application Laid-Open No. 2007-176158 discloses detecting an edge region from a region where an image is to be recorded, and thinning out image data for ink of a predetermined color that correspond to the edge region, in the case of using image data and mask patterns each including one-bit information. According to Japanese Patent Application Laid-Open No. 2007-176158, the amount of the ink of the predetermined color that is discharged onto the edge region of the image can be reduced as compared with the amount of ink discharged onto a non-edge region other than the edge region of the image. Thus, image quality deterioration that is caused by ink bleeding can be suppressed.
Nevertheless, the processing disclosed in Japanese Patent Application Laid-Open No. 2007-176158 is processing performed on image data with which ink can be discharged onto one pixel region only once. Thus, such a technique cannot be applied to correction processing of image data corresponding to an edge region that is performed in the case of using image data with which ink can be discharged onto one pixel region a plurality of times.